<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container{
            width: 100%;
            overflow: hidden;
        }
        .left,.right{
            float: left;
            width: 200px;
            height: 200px;
            line-height: 200px;/*让其文字垂直居中*/
            /*position: relative;*/
        }
        .left{
            background-color: green;
            margin-right: -200px;
            position: relative;
        }
        .center{
            float: left;
            width: 100%;
            background-color: yellow;
            height: 200px;
            line-height: 200px;
        }
        .content{
            margin: 0 200px;/*使center部分内容不被覆盖*/
        }
        .right{
            background-color: blue; 
            margin-left: -200px;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="left">左侧固定</div>
        <div class="center">
            <div class="content">中间自适应</div>
        </div>
        <div class="right">右侧固定</div>
    </div>
</body>
</html>